DE1007991B - Process and device for mixing thermoplastic raw materials with all kinds of additives - Google Patents

Description

GERMAN

The invention relates to a continuous process for automatically controlled mixing of molten polystyrene or other extrudable, thermoplastic masses with one or more modifying agents for the purpose of producing a uniform product. It particularly affects one continuous process for the production of uniformly colored styrene.

It has long been a problem in the production of plastic masses, uniform mixing of plastic masses with one or more materials that exert a special effect, z. B. with dyes, pigments, plasticizers, lubricants, stabilizers, fillers and the like, especially if the ingredients intended for the mixture are not in let dissolve a common solvent, or if it is necessary to carry out the mixture when the plastic masses are either in the molten or in the solid state. An extended one Grinding or treating finely divided plastic mass with any finely divided solid Additive (which is not a dye) in a rotating drum is sufficient in many cases Mixing, especially if the mixture is to be processed using a thermal process, z. B. by ejecting or deforming. However, this is a less satisfactory procedure, when dyes or pigments with normally clear and transparent plastic masses, e.g. B. Polystyrene, should be mixed and especially if the amount of such a coloring Means is low. The difficulty and laboriousness it makes of polystyrene into a fine powder grind, and the prolonged mixing process that is required to achieve a reasonably uniform Preserving color tint helps make the process impractical when there is absolute uniformity is required. Even if you have a uniform mixture of different sized solid particles is obtained, such mixtures tend to move when standing according to their particle sizes settle, with the finer particles usually collecting at the bottom. In the same way, each is Method of making a uniform mixture of solids with molten styrene as a result of the viscous character of the heated molten mass is accompanied by great difficulties. the Widespread use of colored polystyrene has created a need to meet consumer demands for a colored product to satisfy those regarding shade and intensity of the Coloring of the granules of plastic mass, which under different conditions and often from different

Method and device for mixing

thermoplastic raw materials

with all kinds of additives

Applicant:

The Dow Chemical Company,
Midland, me. (V. St. A.)

Representative: Dr.-Ing. H. Ruschke, Berlin-Friedenau,

and Dipl.-Ing. K. Grentzenberg, Munich 13,

Ainmillerstr. 26, patent attorneys

Claimed priority:
V. St. v. America May 27, 1948

Kenneth E. Stober, Midland, Mich. (V. St. A.),
has been named as the inventor

produced by different manufacturers. It is not enough that the average shading a certain amount of particles is the one you want, but it is necessary that all Grains of a lot are of the same shade and intensity of color, and often also that one Coloring matches the previous lots used by the same consumer will. Another practical requirement is that of the various operations involved in manufacturing such mixtures are required to be minimized by having a continuous Process applied so that the size of the equipment used depends on the amount of to be manufactured Mixture becomes independent. To the number of operations in the manufacture of such a To reduce the mixture of polystyrene, it is preferable that the majority of the polymer that is in the mixture occurs, is freshly made, not yet solidified material that is not the costly and requires the time-consuming milling treatment previously required when mixing with different Made additions.

The invention therefore relates to a continuous process for the production of uniform mixtures of polystyrene with different fabrics. This continuous process also enables the production

709 508/442

3 4

Positioning of uniformly colored polystyrene as well as a suitable base concentrate. This concentrated Vorvon colored polystyrenes of uniform mixture is produced by a continuously operating adjustment and color intensity, so that the same weighing device is always used for an ejector is obtained. The invention also relates to several such systems a process that can be fed in a single apparatus without 5 and that is continuous with Consideration of the amount to be processed, low filling and constant output can. The invention also relates to a can be driven so that the mass in this Method of stopping only briefly by any auxiliary ejector. The pre-remedy can pass to another or if the concentrate is mixed in the ejector that, using the same additive, melted its io and thence immediately without cooling Proportions can be reduced without being fed or fed to a larger ejection device stop driving. a mixer in which continuously a lot

According to the present invention, the previously provided thermoplastic mass can be added The following and related objectives are achieved by polymers, preferably in the molten state, and a perfectly uniform blend of poly-15 is introduced. The larger ejector is styrene or other ejectable thermoplastic of a type with variable speed masses can be operated with common additives (e.g. color and speed and is with an output filler, Stabilizers, plasticizers, etc.), opening for the purpose of producing a thin, preferred agent the method described below as flat belt of the polymer equipped. That produce. One takes a small amount of the pressed tape and goes between the plates of one powdered or granular thermoplastic material, high frequency AC capacitor through it, that of the total amount of mixture to be made and the slightest change in the thickness of the stands in a certain ratio, and mixes the tape and thus the dielectric also changes the this intensively with the desired substance in the capacitance of the capacitor. Such change a ratio that you get a much higher 25 is immediately recorded and immediately means Concentration of the substance in this mixture is given a motor-driven resistance circuit in the than one wishes to have in the end product, e.g. B. Power line to which the variable Ge-20- up to 50 times as high. Usually the speed-running engine is connected, which is beneficial largely uniform powdered concentration, so that the ejected tape is always on the entered in the form of strips or in pellets of the desired uniform thickness, of lighter size. These beads are used in the desired ratio of the additive to the thermoeiner rotating drum treated and mixed, plastic mass is therefore paused so that in order to obtain a uniform distribution of the globules one the ejection quantity from the larger ejection among themselves to obtain the individual copies of which device the feed quantities of the premixed added more or less an average amount of the concentrate to the small ejector Substance included. As a result, the unit fits and then maintains this relationship. If the Borrowed size of the beads finds no further desired amount of modifier in the physical self-plasticization takes place, itself not numerically known in advance, so one can with the when standing for a long time, and the ejector device, which is larger than the pellets, easily increases this ratio If you use the following equation:

Known percentage of additive in the premix

= Required total discharge amount to the known on-Desired percentage of the additive in the final product of the premix _ga bemenge

The amount of premixed concentrate must match the discharge port. With an effective form be chosen so that the required total output - the mixing head has a number of rotating throughputs always remains smaller than the maximum power of the perforated disks, which in extension of the axis large ejector capability. the ejector screw are mounted with in between

When the desired amount of additives is still 50 arranged solid, perforated plates, It is not known who the particular changes to the The invention is to be based on the drawing the ejected mass cause to be made understandable. The figure shows in a can, as is the case when color intensity in schematic representation of the flow of materials colored samples or samples mixed with a pigment through the system and the control agents used in the is compared, the ejection rate from the method will be applied.

large ejector gradually changed until a concentrate mixture of sufficiently fine one Examination of the product shows that a ground polystyrene and the desired additive suitable match has been achieved; this is where fabric is produced. You can do this in that way the process is now monitored in such a way as to cause the individual components to be added ejection rate set in this way remains the same. 60 together in a mixing device, e.g. B. in a

The larger ejector from which the belt rotating drum 1, treated or in any of the mixed product is discharged, has another suitable way to get a dry, free Mixing head to make the mixing, the normally flowing mixture of sufficiently uniform along the composition in a plastic ejector, and one can Screw conveyor is going to increase. Process many 65 into beads as described above, Such systems are known, with most of them a This concentrate is made by one according to the vibra mechanism provided, in which the flows of the feeding device operating principle 2 Polymers separate one or more times and come back to one another at a steady rate are mixed with each other, usually fed evenly because of the conveyor belt 3, between the screw conveyor of the ejector 7 ° This conveyor belt is on an automatic

Weighing device 4 attached, which is shown in the drawing as a scale with two weighing pans. The weight on the second shell is measured so that a balance is achieved when the Weight of the concentrate on the conveyor belt of the desired hourly feed rate of the concentrate is equivalent to the ejection system. If too much concentrate falls on the conveyor belt, so the opposite weighing bowl lifts and

uniform mixture of one of them different To change the compilation.

In a particular example, a premixed concentrate was made by 5 22.7 kg of titanium dioxide pigment and 68 kg of clear small granules of polystyrene in a rotating cylinder worked until the mixture was approximately uniform.

This mixture was activated in the form of a fine stream of a switch which temporarily pushed off the vibrator and set it into uniform spheres of about and thus the inflow of the concentrate. Cut to 3 mm thick. These were turned in a reversal, if too little concentrate is processed on the transport rotating drum, around the bead band falls, the opposite shell is lowered evenly to distribute the average and actuated the switch, causing the vibrator to deviate in the composition of the concentrate. That is set in motion, the concentrate processed in this way on 15 pellets was then dropped on the conveyor belt. The concentrate falls at a constant speed of 7.25 kg from the conveyor belt directly through the hour from a vibrating feeder and funnel into the transport screw of an ejector operated at constant speed, an automatic weighing device, as described in a screw ejector 5 from small content, in which the plastic 20 promotes, the mass worked at constant speed is melted and from which the concentrate and 6.35 cm Durohmesser had. The concentrate in the container of a larger ejector 6 was ejected from this ejector as a stream conveying an abundant supply of molten mass into the container of an ejecting plastic mass to be modified as a device that was 15.2 cm in diameter main feed mass receives. One or more can be provided with a drive device that can use and be able to use other vibratory feeders and the automatic scales connected to them that are operated at a variable speed. The larger ejector with also one or more of the constant-speed ejectors with a diameter of 15 cm was provided for continuously operating ejectors, in clear, molten polystyrene under constant pressure which was borrowed from a wood-coated concentrate with the same or different pressure works as it is necessary, supplied to the storage tank, which in turn immediately to obtain the desired final mixture. Each was fed from a polymerization vessel. The concentrate with the plastic mass in the larger ejector was equipped with a mixing screw conveyor of the large ejector head, and the colored polystyrene emerged from being diluted and mixed and is further in a 35 of it as a belt of 20.3 cm wide and 3 mm thickness mixing head 7 in order to achieve a uniform from, and in an amount of 181 kg processed in the mixture. This is shown as an hour in the drawing. As shown, the ejected tape passed through a series of perforated, alternately rotating, between the plates of a capacitor, and solid disks shown. The so mixed _and every change in dimensions was immediately plastic mass is ejected as a thin band 8, transmitted 40 bar and caused changes in which it passes between capacitor plates 9 on the way to the ejection speed of the variable-speed cutting device 10 in the mixing device operating at speed . The feed rate, by known means, of the concentrate, brought to 25% to contain pigment for ejection or deforming purposes, became 7.25 kg per hour to serve as feed material. The capacitor is a 45 constant and the end product at 181 kg in part of a high-frequency circuit, which with one of the hour, whereby one got a uniformly white display device 11 and a control device, which is exactly 1% titanium dioxide dye 12 of a known type is connected. The lightest contained.

Change the size of the dielectric (the plastic). For a different sample, a special

see mass) that goes through between the plates, 50 shading of an opaque ivory color causes an immediate response of a motor-gearbox- can be achieved in polystyrene. This shading creates resistance in the power line to the engine,
which drives the screw of the large ejector and makes the ejection speed instantaneous
is corrected and the desired dimensions 55
of the ejected tape can be restored.
If in the concentrate or concentrates
there is a fixed ratio of the components and
a fixed rate of delivery of the concentrates to the with

ejector working with a low content before 60 as described above, processed into beads. the is seen and a fixed rate of ejection of beads of each concentrate were made in a rotiedort treated to the larger mixing ejector drum and so a distribution will see, _ so it can be seen that the erect of the globules obtained deviated from the average, maintaining a constant output rate from the Then each concentrate was made from a special one larger ejector a unitary pro 65 vibratory feeder assigned to one product can be produced for any length of time, and since it is routed to and from every automatic weighing device Time only a small amount of admixed over a special small, with constant speed substances is present, you only have a very short time working squeezer in an off-time needs to feed the system from the one fabric pressing device of 15.2 cm in diameter, clean up and the production on another, equal 70 which in turn a continuous and plentiful supply

had white, yellow and red components. Three individual concentrates were used in the preceding Example described type manufactured:

1. Clear polystyrene 68 kg, titanium white 9.06 kg.

2. Clear polystyrene 90.6 kg, cadmium red 0.23 kg.

3. Clear polystyrene 88.34 kg, cadmium lithopone (lemon yellow) 0.9 kg.

Each concentrate was mixed, squeezed and,

drove from molten polystyrene obtained under constant pressure. The white concentrate was made with a Speed of 8.60 kg per hour. The red concentrate at a speed of 7.8 kg per hour and the yellow concentrate at a rate of 4.32 kg to the desired Create shading as well as the desired color intensity in the finished product, which is considered to be thin Tape 20.3 cm wide is pressed out at a rate of 181 kg per hour. That Product contained 0.475% titanium white, 0.0102% red pigment and 0.024% lemon yellow pigment, and this condition was automatically made by means of the system operated by the condenser for the Maintain control of the speed of the large ejector. After the desired Amount of the ivory-colored product had been obtained, a new series of Concentrates put in place of those previously used to create a new shade that is within of 30 minutes, during which time all of the system was left over from all Traces of the white, red and yellow concentrate had been cleaned.

The measure described in the last example, after which each dye for itself (or any other additive) is added as a concentrate through a special feeding and weighing system, simplifies the process of color mixing. But it is just as possible to use a single concentrate to produce containing all the necessary modifying ingredients. But you can also do one Mix a plurality of premixed concentrates together and the resulting product from one single feed device and via a single ejector into the large ejector or convey an equivalent apparatus in which it is continuous with the plastic to be modified Mass is mixed.

In the examples is the introduction of measured amounts of pigments into molten polystyrene has been described. Dyes, plasticizers or other modifying agents can be used in the same way be added to this or other extrudable thermoplastic compositions, e.g. B. to copolymers from vinyl chloride acetate, ethyl cellulose, vinylidene chloride copolymers, styrene - α - methylstyrene copolymers and the like. The major amount of plastic material to be modified has been described herein as a molten mass, but at suitable mixing capacity of the larger mixing ejector, the feed quantity can be in the form of of powders or granules composed of the plastic mass are supplied.

Claims (5)

Patent claims: 1. Process for the continuous production of uniform mixtures of polystyrene with additives, characterized in that a screw conveyor in constant amounts is a uniform premixed concentrate of polystyrene with at least one of the usual additives (Dye and filler, stabilizer, softener and the like.) And that the concentrate in constant amounts that correspond to the supply amount, another, considerably larger mixing plant with a screw conveyor in which a lot of polystyrene is added to the concentrate is admixed, which is the desired final ratio of additives to polystyrene produces that the mixture thus formed is then ejected from the zone as a thin band, A high-frequency voltage is continuously applied to it in order to measure its electrical capacitance and at the same time to regulate the ejection speed according to the occurring capacity changes. 2. The method according to claim 1, characterized in that the premixed concentrate of the Polystyrene mixed with molten polystyrene in the advanced mixer and conveyor will. 3. The method according to claim 1 or 2, characterized in that each premixed concentrate contains 20 to 50 times the amount of additives that can be obtained in the desired final concentration in the Desires to obtain polystyrene. 4. The method according to claim 1 or 2, characterized in that a plurality of premixed Concentrates are used, each of which has a different color component of the desired final color contains and is fed individually. 5. Plant for the continuous production of mixtures of molten, plastic masses, consisting of a) a conveying and ejecting device to prepare a premixed concentrate plastic mass and additives with constant feed rate of a larger mixing and feed device and to this concentrate with further quantities of starting material to bring it to the desired final concentration, b) from a high-frequency capacitor, the plastic mass is passed between the plates as a thin band, and c) from Take precautions to reduce the concentration changes indicated by changes in the capacitor capacity, the mixing speed and the output quantity to be regulated in the larger mixing and discharge vessel. 1 sheet of drawings © 709 508/442 4.57